Solid block of propellant with a plurality of propulsion stages and methods of manufacture

ABSTRACT

A solid propellant block comprises several successive powder layers, whose principal ingredient is nitrocellulose, burning in sequence and having planar, cylindrical or other contact surfaces, the layers being sealed to one another at the contact surfaces by gelatinization of the nitrocellulose by nitroglycerine, a polyalcohol nitrate or an explosive oil base molding solvent, which is another ingredient of at least one of the powder layers.

United States Patent 11 1 Humbert et al.

14 1 Dec. 16,1975

[54] SOLID BLOCK OF PROPELLANT WITH A PLURALITY OF PROPULSION STAGES AND METHODS OF MANUFACTURE [75] Inventors: Jean Jacques Humbert; Jean Pierre Francis Thomas; Gerard Yvan Brut;

Jean Marie Joseph Elie Gounou, all

of Paris, France [73] Assignee: Societe Nationale des Poudres et Explosifs, France 22 Filed: Oct. 15, 1969 [21 Appl. No.2 866,621

[30] Foreign Application Priority Data Oct. 15, 1968 France 68.169952 [52] US. Cl. 149/14; 102/100; 102/103; 149/2; 149/97; 149/98; 264/3 R [51] Int. Cl. C06B 45/12 [58] Field of Search 149/14, 97, 98; 264/3 R; 102/100, 101, 103; 156/286, 287

[56] References Cited UNITED STATES PATENTS 1,316,360 9/1919 Delpech 149/14 Dallett 102/100 Lichfield 1. 156/286 X FOREIGN PATENTS OR APPLICATIONS 16,858 7/1897 United Kingdom 149/14 27,397 2/1898 United Kingdom..... 149/14 28,376 3/1905 United Kingdom 149/14 Primary Examiner-Leland A. Sebastian Attorney, Agent, or Firm-Bucknam and Archer [57] ABSTRACT 15 Claims, 4 Drawing Figures US. Patent Dec. 16,1975 Sheetlof4 3,926,697

F/G.l

Patent Dec. 16, 1975 Sheet 2 0f 4 Sheet 3 0f 4 U.S. Patent Dec. 16, 1975 US. Patent Dec. 16, 1975 Sheet4of4 3,926,697

SOLID BLOCK OF PROPELLANT WITH A PLURALITY OF PROPULSION STAGES AND METHODS OF MANUFACTURE This invention relates to self-propelled devices and particularly to the propellant composition thereof and methods of producing such propellant compositions.

Self-propelled devices generally comprise several, often two, propulsion stages, called acceleration stages and cruising stages. In modern devices, an object is to combine these stages in a single combustion chamber so as to obtain a single-chambered propulsion device with several stages of lift. The advantage of such a construction is that these devices can be of light construction.

However, rarely can all the required left requirements be attained with a single composition of propellant. For such purpose the propellant would have to have a very long whole-time level of its speed vs. pressure curve (its speed of combustion must therefore be constant over a very wide pressure interval) or a series of whole-time levels placed precisely in the anticipated fields of combustion and pressure.

This difficulty can be avoided by selecting a suitable propellant composition for each stage of lift. But it is then necessary to place several separately manufactured blocks of powder into a single combustion chamber and provide means for them to burn in their proper sequence. These blocks must therefore be adhesively joined to one another in such a way that the surface under combustion has the required section.

The adhesives behave as partial inhibitors, so that drastic drops of pressure, known as pressure troughs are noted when the combustion crest traverses an adhesion surface. This makes guidance of self-propelled vehicles by tail units impossible.

Such a method offers numerous other drawbacks, among which the following may be specially noted:

a. impaired safety on prolonged storage or at high temperatures as the adhesively joined surfaces have a tendency to come apart;

b. impossibility of shaping the adjoining blocks at the surface of adhesion (which has to be machined with extreme precition on each of the blocks in contact); and

0. high cost of manufacture as a consequence of the precision machinery required.

An object of the present invention is to provide a solid block of two or more propellant compositions with different ratings of lift, comprising successive layers of powders, whose principal ingredient is nitrocellulose, burning in sequence and having planar, cylindrical or other partition surfaces. These layers adhere to one another at such partition surfaces by gelatinization of the nitrocellulose by nitroglycerine, polyalcohol nitrate or explosive oil-base molding solvent, which is a further ingredient of at least one of these layers.

According to one particular method of application, the powders are of double-base type, each layer being composed of one so-called base powder (granular forms of stabilized nitrocellulose containing also ballis tic additives and plasticizers) different from that in the next adjacent layer and a molding solvent identical to that in the said next adjacent layer.

According to one variant, each layer is composed of a so-called base powder, different from that in the next adjacent layer, and a molding solvent different from that in the said next adjacent layer.

2 According to another variant, at least one of the layers is composed of a block of extruded double-base powder while the remaining layer or layers are composed of different basic powders and one molding solvent is used throughout, or different molding solvents are used.

BRIEF DESCRIPTION OF THE DRAWING:

FIG. I is a side view in section, of a mold according to the invention in one stage of operation;

FIG. 2 is a perspective view of the moldof FIG. 1, partly broken away, in another stage of operation;

FIG. 3 is a perspective view of a mold employed in a preliminary step of forming a multi-layer block; and

FIG. 4 is a perspective view of the mold of FIG. 3 in a later step of forming the multi-layer block.

DETAILED DESCRIPTION OF THE INVENTION:

The solid propellant block of dual or multiple layers can be manufactured according to the invention by a single pour operation or by successive pouring operations.

The manufacture of the propellant blocks by these different pouring techniques according to the invention is described in the following non-restrictive examples:

EXAMPLE 1 In this example a solid block of a two layer propellant is manufactured by the single pour technique.

For this purpose the following so-called basic powders and molding solvent are used: A Composition of the basic powder for the acceleration layer weight 12.6% nitrogen nitrocellulose 92.5 Centralite (stabilizer) 1.5 Methyl phthalate (plusticizer) 3.0 Lead stearate (combustion catalyzer) 1.5 Acetylene black (combustion accelerator) 1.5

B Composition of the basic powder for the cruising layer 7: by weight 12.6% nitrogen nitrocellulose 90.0 Centralite 2.0 Methyl phthulate 5.0 Lead stearate 3.0

C Composition of the molding solvent 7: by weight Nitroglycerine 78.0 Triacetin (phlegmatizer) 21.5 Centralite (stabilizer) 0.5

The mold employed to form the solid two layer block is shown in sectional elevation in FIGS. 1 and 2 of the drawing, and comprises a tubular body I provided at its lower end with a filter plate 2 and a wire gauze 3. A spindle 4 of star-shaped cross-section and a separator tube 5 are located inside the body 1. Centering of the separator tube, which is made, for instance, of a cylindrical sheet of foil, is effected by means of engagement of the separator tube in a groove 2a machined in plate 2 and in a star-shaped metal ring 6. Centering of spindle 4 is effected by means of a bearing 2b provided on plate 2 and a star-shaped stop 7 of inert plastic mate rial. The separating tube thus divides the inside of the mold into two annular concentric chambers 8 and 9 adapted for receiving the powders of composition A and B respectively.

The lower end of the mold 1 is consolidated with a shoulder 10, which is provided with a molding solvent inlet 11 and an air inlet 12 both opening into a lower chamber 13.

The two chambers 8 and 9 are filled simultaneously with granules of the basic powder composition A and of the basic powder composition B respectively described above, so as to avoid buckling of separator tube 5, and for this purpose a two-compartment filling hopper 14 is employed which feeds chambers 8 and 9 respectively as shown in FIG. 1.

After filling the mold, the separator tube 5 is carefully withdrawn perfectly parallel with the centerline of the mold, so that the partition surface between the basic powders is not disturbed.

Then after a filter plate 15 and tiepiece 16 have been fitted as shown in FIG. 2, the loaded mold is closed with a hermetic lid 17 and a vacuum is produced in the mold. The molding solvent of the composition C as defined above is introduced at 35C. through inlet 11 to fill the interstices between the basic powder granules. After filling, the vacuum is broken and the entire mass in the mold is subjected to a heating program including maturation at 45C for 24 hours, then baking at 65C for 96 hours. This results in gelatinization of the nitrocellulose by the molding solvent in the presence of the nitroglycerine. The two-layer propellant block is then removed from the mold and cut into pieces of the required length, after which it is faced up and varnished.

Because the junction of the two layers of the doublebase powders constituting the dual composition solid block of propellant is obtained by gelatinization of the nitrocellulose by the molding solvent, a remarkable continuity in the pyrotechnic chain is obtained and no disturbance (pressure troughs) is observed when the flame front passes through the cylindrical partition surface of the said layers. Moreover, such a junction is greatly resistant to storage and hot climates.

Polyalcohol nitrates can also be used as the molding solvent, particularly diethyleneglycol nitrate; also usable as the molding solvent are the known explosive oils.

A solid block of dual composition propellant with planar partition faces can be obtained by using a square or rectangular section mold with a planar separating partition in the simple pour process above described.

However, if the separating partitions are neither planar nor cylindrical, it is not possible to withdraw them without disrupting their shape before the molding solvent is introduced; likewise, if the different powder compositions comprise different molding solvents, such solvents cannot be introduced all at the same time into the mold. The procedure then comprises successive pourings and one or more portions of the body to be produced are made beforehand in a mold of suitable shape. Then if the filling is of the dual composition type, a pre-formed layer with the first basic powder is introduced as a form into the master mold, and filling again proceeds with the second basic powder. If the filling is of the multiple composition type, the procedure comprises pre-forming a plurality of layers with the powder of one of the compositions, filling the spaces between these layers with the other basic pow- EXAMPLE 2:

The basic powder composition A and molding solvent composition C as specified in Example 1 are used for the acceleration layer, and basic powder composition D and molding solvent composition E given below are used for the cruising layer.

D Composition of the basic powder for the cruising layer weight 12.6% nitrogen nitrocellulose 90.0 2-nitrodiphenylamine (stabilizer). 2.0 Octyl phthalate (plasticizer) 50 Lead stearate 3.0

E Composition of the molding solvent for the cruising layer 7: by weight 72.0 27.0 l.0

Nitroglycerine Triacetine (phlegmatizer) Z-nitrodiphenylamine (stabilizer) The cruising layer is poured first, using a mold similar to that described for Example 1 but without a separator tube 5 but with a spindle 4 of a diameter equal to the internal diameter of the cruising layer.

The mold is then filled with the basic powder composition D, after which the mold is closed, subjected to vacuum and supplied with molding solvent E. The vacuum is terminated and the mass is subjected to a partial baking program for 24 hours at 45C, then 30 hours only at 65C. Thereafter, the cast portion is removed from the mold, and its slightly rough inside surface (0.1 mm deep wrinkles) is cleaned to remove any possibility of interference with proper adhesion or the formation of a cling layer.

The cruising layer 18 thus cast is inserted as a form in the master mold 1 (FIG. 4) identical to the one described in Example 1 but without the separator tube 5. Central spindle 4 is then placed in position and the space between spindle 4 and layer 18 is filled with granules of composition A. The mold is closed, subjected to vacuum and then molding solvent C is introduced into composition A. The vacuum is then terminated and the entire mass is subjected to a baking program as in Example 1.

During this baking, there is a gelatinization of the powder granules D coating the inside face of the layer 18 first poured but only partly baked, on contact with the new molding solvent C, and these grains become welded to the gelatinized grains of the powder A.

EXAMPLE 3 In this example the successive pouring technique is used, but with a block of extruded double-base powder known as SD (without solvent) powder of the following composition, as an acceleration layer.

F Composition of the SD powder weight 1 l.7% nitrogen nitrocellulose 67.6 Nitroglycerine 20.8 Centralite 3.0 Ethyl phthalate 5.6 Lead stearute 3.0

This block is placed as a form in a master mold of the type described in Example 2 and the mold is filled with basic powder D specified in Example 2, whereafter molding solvent E (also specified in Example 2) is introduced so as to form the cruising layer. The entire mass is then subjected to the baking program in Example 2.

What is claimed is:

l. A method of producing a solid propellant block comprising a plurality of successive concentric adjacent layers of different compositions adapted to burn in sequence to provide successive stages of lift, each layer being bonded to adjacent layers by gelatinized nitrocellulose, which comprises forming a plurality of contacting adjacent layers of different compositions in a mold, each layer consisting of a propellant composition comprising nitrocellulose as the principal ingredient, at least one of said adjacent layers consisting of granules of a base powder of a propellant composition the principal ingredient thereof being nitrocellulose, introducing a molding agent comprising nitroglycerine or a. polyalcohol nitrate as the principal ingredient, under vacuum into at least said layer consisting of said base powder to cause at first flow of said nitroglycerine or said polyalcohol nitrate into the interstices between the granules of said base powder and heating in the mold at a temperature and for a period of time sufficient to cause molding of said base powder in situ and gelatinization of the nitrocellulose of said base powder and at the contact surface of the adjacent layers thereof, whereby said layer formed from said base powder is sealed to its adjacent layers by means of said gelatinized nitrocellulose.

2. The method according to claim 1 wherein said contact surface is planar.

3. The method according to claim 1 wherein said contact surface is cylindrical.

4. The method according to claim 1 wherein heating is carried out at 45C for 24 hours followed by heating at 65C for 96 hours.

5. The method according to claim 1 wherein one of said adjacent layers is a double base cast powder and the other is an extruded double base powder.

6. A method of producing a propellant block in accordance with claim 1 wherein a plurality of adjacent layers are molded in situ from dissimilar base powders and said adjacent layers are fonned by placing a separating partition in the mold to form separate chambers for said adjacent layers, pouring the base powder composition of each layer into the respective chambers, removing the partition while leaving the contact surface between the adjacent layers undisturbed, introducing said molding agent under vacuum and thereafter heating the layers to effect gelatinization and sealing.

7. A method of producing a propellant block in accordance with claim 5 wherein said molding agent is introduced simultaneously into all said layers.

8. A method of producing 'a propellant block according to claim 1 wherein at least one of the adjacent layers is a preformed block, which comprises introducing said preformed block into a mold, the preformed block being of such size that vacant regions remain in the, mold, introducing a different composition the principal component of which is nitrocellulose in granular form into the vacant regions of the mold, to form said adjacent layer, with said pre-formed block serving as a form for a chamber for said adjacent layer, whereafter introducing a molding agent for said adjacent layer into said mold and heating the entire mass to effect the gelatinization of nitrocellulose and sealing at the contact surfaces.

9. The method according to claim 8 wherein heating is carried out at 45C for 24 hours followed by heating at 65C for 30 hours to achieve partial gelatinization of said preformed layer and in the final step heating is carried out at 45C for 24 hours followed by heating at 65C for 96 hours.

10. The method according to claim 8 wherein said preformed block is a composition containing said molding agent.

11. A method of producing the block of claim 8 wherein a plurality of said blocks are pro-formed and placed in said mold.

12. The method as claimed in claim 11, wherein the molding agent comprises 72-78% nitroglycerine, 21-27% triacetin and 0.5-l% stabilizer.

13. A solid block of propellant prepared by the method of claim 1.

14. A solid block of propellant prepared by the method of claim 6.

15. A solid block of propellant prepared by the method of claim 8. 

1. A METHOD OF PRODUCING A SOLIDPROPELLANT BLOCK COMPRISING A PLURALITY OF SUCCESSIVE CONCENTRIC ADJACENT LAYERS OF DIFFERENT COMPOSITIONS ADAPTED TO BURN IN SEQUENCE TO PROVIDE SUCCESSIVE STAGES OF LIFT, EACH LAYER BEING BONDED TO ADJACENT LAYERS BY GELATINIZED NITROCELLULOSE, WHICH COMPRISES FORMING A PLURALITY OF CONTACTING ADJACENT LAYERS OF DIFFERENT COMPOSITIONS IN A MOLD, EACH LAYER CONSISTING OF A PROPELLANT COMPOSITION COMPRISING NITROCELLULOSE AS THE PRINCIPAL INGREDIENT, AT LEAST ONE OF SAID ADJACENT LAYERS CONSISTING OF GRANULES OF A BASE POWDER OF A PROPELLANT COMPOSITION THE PRINCIPAL INGREDIENT THEREOF BEING NITROCELLULOSE, INTRODUCING A MOLDING AGENT COMPRISING NITROGLYCERINE OR A POLYALCOHOL NITRATE AS THE PRINCIPAL INGREDIENT, UNDER VACUUM INTO AT LEST SAID LAYER CONSISTING OF SAID BASE POWDER TO CAUSE AT FIRST FLOW OF SAID NITROGLYCERINE OR SAID POLYALCOHOL NITRATE INTO THE INTERSTICES BETWEEN THE GRANULES OF SAID BASE POWDER AND HEATING IN THE MOLD AT A TEMPERATURE AND FOR A PERIOD OF TIME SUFFICIENT TO CAUSE MOLDING OF SAID BASE POWDER IN SITU AND GELATINIZATION OF THE NITROCELLULOSE OF SAID BASE POWDER AND AT THE CONTACT SURFACE OF THE ADJACENT LAYERS THEREOF, WHEREBY SAID LAYER FORMED FROM SAID BASE POWDER IS SEALED TO ITS ADJACENT LAYERS BY MEANS OF SAID GELATINIZED NITROCELLULOSE.
 2. The method according to claim 1 wherein said contact surface is planar.
 3. The method according to claim 1 wherein said contact surface is cylindrical.
 4. The method according to claim 1 wherein heating is carried out at 45*C for 24 hours foLlowed by heating at 65*C for 96 hours.
 5. The method according to claim 1 wherein one of said adjacent layers is a double base cast powder and the other is an extruded double base powder.
 6. A method of producing a propellant block in accordance with claim 1 wherein a plurality of adjacent layers are molded in situ from dissimilar base powders and said adjacent layers are formed by placing a separating partition in the mold to form separate chambers for said adjacent layers, pouring the base powder composition of each layer into the respective chambers, removing the partition while leaving the contact surface between the adjacent layers undisturbed, introducing said molding agent under vacuum and thereafter heating the layers to effect gelatinization and sealing.
 7. A method of producing a propellant block in accordance with claim 5 wherein said molding agent is introduced simultaneously into all said layers.
 8. A method of producing a propellant block according to claim 1 wherein at least one of the adjacent layers is a preformed block, which comprises introducing said preformed block into a mold, the preformed block being of such size that vacant regions remain in the mold, introducing a different composition the principal component of which is nitrocellulose in granular form into the vacant regions of the mold, to form said adjacent layer, with said pre-formed block serving as a form for a chamber for said adjacent layer, whereafter introducing a molding agent for said adjacent layer into said mold and heating the entire mass to effect the gelatinization of nitrocellulose and sealing at the contact surfaces.
 9. The method according to claim 8 wherein heating is carried out at 45*C for 24 hours followed by heating at 65*C for 30 hours to achieve partial gelatinization of said preformed layer and in the final step heating is carried out at 45*C for 24 hours followed by heating at 65*C for 96 hours.
 10. The method according to claim 8 wherein said preformed block is a composition containing said molding agent.
 11. A method of producing the block of claim 8 wherein a plurality of said blocks are pre-formed and placed in said mold.
 12. The method as claimed in claim 11, wherein the molding agent comprises 72-78% nitroglycerine, 21-27% triacetin and 0.5-1% stabilizer.
 13. A solid block of propellant prepared by the method of claim
 14. A solid block of propellant prepared by the method of claim
 6. 15. A solid block of propellant prepared by the method of claim
 8. 